Reversi Online — Play Othello vs Computer
Flip your opponent’s discs to own the board. Pass-and-play or a positional AI across four difficulty levels, with legal-move hints.
Reversi · Othello
Out-flank to flip. Hold the corners. End with the most discs.
Black always makes the first move. Pick White to let the computer open.
A move is legal only if it sandwiches at least one straight line of opponent discs between the disc you place and another of your own — every flanked disc flips to your colour. No legal move? You pass. When neither side can move the game ends and the majority wins.
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About Reversi Online — Play Othello vs Computer
Play Reversi — the disc-flipping strategy game standardised as Othello — free in your browser, against the computer or with a friend in pass-and-play on one screen. The rules are faithful to the modern game: Black moves first from the standard diagonal centre setup, a move is only legal if it outflanks at least one straight line of enemy discs, every flanked disc flips to your colour, you pass when you have no legal move, and when neither side can move the player with the most discs wins.
The four computer levels are genuinely different opponents, not just timers. Easy plays random legal moves, Medium greedily grabs the most flips, Hard plays positionally using a weighted board map that prizes corners and punishes the poisonous squares beside them, and Expert runs a minimax search with alpha-beta pruning — looking four to six moves ahead and judging positions on board weights, mobility and corner control. Legal-move hints, undo, a live disc count and animated flips make it a friendly place to learn; the board is even fully keyboard-playable with arrow keys and Enter.
Reversi rewards a beautiful counter-intuition: hoovering up discs early usually loses. Discs only count at the very end — through the mid-game what matters is mobility (keeping more options than your opponent) and the corners, which can never be flipped once taken. Learn to keep your disc count low, avoid the X-squares diagonally touching empty corners, and you will start beating the Hard computer.
Popular uses
Frequently asked questions
They are essentially the same game. Reversi is the older 19th-century English game; Othello, trademarked in Japan in the early 1970s, standardised the rules most people play today — a fixed diagonal starting position in the centre and Black always moving first. This game follows the Othello convention, which is why choosing White lets the computer open.
Because discs only score at the end and can be flipped back many times before then. A big early wall of your colour gives the opponent more landing squares (mobility) while starving you of moves, forcing you into bad squares later. Strong players deliberately keep their disc count low through the mid-game — you can watch this idea in action by beating Medium (which plays greedily) with fewer early discs.
A corner disc can never be outflanked, so it is permanently yours and anchors stable, unflippable edges growing out of it. The positional AI here values a corner at +120 while the X-squares diagonally adjacent to an empty corner score −40, because playing them usually hands the corner to your opponent. That one heuristic — take corners, shun X-squares — is most of what separates Hard from Medium.
They pass, and the opponent moves again — the game announces the pass so nobody is confused. Passing is only allowed when you truly have no legal move (the move counter shows how many you have). The game ends when neither player can move, which can happen before the board is full; whoever has more discs at that point wins, and equal counts are a draw.
Expert uses depth-limited minimax with alpha-beta pruning: four plies of look-ahead in the mid-game, deepening to five or six as the board empties, over an evaluation that blends positional weights, mobility and corner occupancy. It punishes casual mistakes reliably and is a solid training partner for improving players, though it is intentionally beatable — it is not an endgame-perfect engine.
Reversi Online — Play Othello vs Computer is 100% free — no signup, no watermarks and no usage limits. It’s one of 200+ free tools we build and give away.
Yes — best scores save in your browser and most games give you a shareable result to challenge friends.
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